A lawn mower's transmission can suffer when air gets trapped in the hydraulics. This problem often occurs when the mower is shipped, so it's often a good practice to purge the mower's transmission prior to the initial use. You can get your Husqvarna lawn mower into proper operating condition following a transmission purging regardless of your familiarity with this troubleshooting routine.
Position the Husqvarna mower on a level surface. Ensure the engine has been shut off.
Pull the mower's transport lever out.
Turn the engine on and set the emergency brake.
Put the throttle lever into its "Slow" setting. The throttle lever in on the left side of the driver's seat. Ensure the mower is in "Neutral."
Push the motion control lever on the dashboard to the full forward position. Leave it in this position for five seconds.
Pull the Husqvarna's motion control lever to the full reverse position. Keep the control lever in this position for five seconds.
Repeat the move from full reverse to full forward position on the motion control lever three separate times, keeping the lever in each position for five seconds. This will purge the air from the Husqvarna's hydraulics.
Turn off the Husqvarna's engine and push the transport lever back in.